Buggy code:
public final class RedisBungee extends Plugin { private static Configuration configuration ; @ Getter private static Gson gson = new Gson ( ) ; private static RedisBungeeAPI api ; private static RedisBungee . PubSubListener psl = null ; @ Getter private JedisPool pool ; @ Getter private UUIDTranslator uuidTranslator ; @ Getter private String serverId ; @ Getter private DataManager dataManager ; @ Getter private ExecutorService service ; private List < String > serverIds ; private AtomicInteger nagAboutServers = new AtomicInteger ( ) ; private ScheduledTask integrityCheck ; private ScheduledTask heartbeatTask ; public static RedisBungeeAPI getApi ( ) { } static Configuration getConfiguration ( ) { } static RedisBungee . PubSubListener getPubSubListener ( ) { } final List < String > getServerIds ( ) { } final List < String > getCurrentServerIds ( ) { Jedis jedis = pool . getResource ( ) ; try { int nag = nagAboutServers . decrementAndGet ( ) ; if ( nag <= 0 ) { nagAboutServers . set ( 10 ) ; } ImmutableList . Builder < String > servers = ImmutableList . builder ( ) ; Map < String , String > heartbeats = jedis . hgetAll ( "heartbeats" ) ; for ( Map . Entry < String , String > entry : heartbeats . entrySet ( ) ) { try { <START_BUG> long stamp = Long . valueOf ( entry . getValue ( ) ) ; <END_BUG> if ( ( System . currentTimeMillis ( ) ) < ( stamp + 30000 ) ) servers . add ( entry . getKey ( ) ) ; else if ( nag <= 0 ) { getLogger ( ) . severe ( ( ( ( ( entry . getKey ( ) ) + "<seq2seq4repair_space>is<seq2seq4repair_space>" ) + ( ( System . currentTimeMillis ( ) ) - stamp ) ) + "ms<seq2seq4repair_space>behind!<seq2seq4repair_space>(Time<seq2seq4repair_space>not<seq2seq4repair_space>synchronized<seq2seq4repair_space>or<seq2seq4repair_space>server<seq2seq4repair_space>down?)" ) ) ; } } catch ( NumberFormatException ignored ) { } } return servers . build ( ) ; } catch ( JedisConnectionException e ) { getLogger ( ) . log ( Level . SEVERE , "Unable<seq2seq4repair_space>to<seq2seq4repair_space>fetch<seq2seq4repair_space>all<seq2seq4repair_space>server<seq2seq4repair_space>IDs" , e ) ; if ( jedis != null ) pool . returnBrokenResource ( jedis ) ; return Collections . singletonList ( serverId ) ; } finally { pool . returnResource ( jedis ) ; } } final Multimap < String , UUID > serversToPlayers ( ) { } final int getCount ( ) { } final Set < UUID > getLocalPlayers ( ) { } final Collection < String > getLocalPlayersAsUuidStrings ( ) { } final Set < UUID > getPlayers ( ) { } final Set < UUID > getPlayersOnServer ( @ NonNull String server ) { } final void sendProxyCommand ( @ NonNull String proxyId , @ NonNull String command ) { } final void sendChannelMessage ( String channel , String message ) { } @ Override public void onEnable ( ) { } @ Override public void onDisable ( ) { } private void loadConfig ( ) throws IOException , JedisConnectionException { } class PubSubListener implements Runnable { private Jedis rsc ; private RedisBungee . JedisPubSubHandler jpsh ; private PubSubListener ( ) { } @ Override public void run ( ) { } public void addChannel ( String ... channel ) { } public void removeChannel ( String ... channel ) { } public void poison ( ) { } } class JedisPubSubHandler extends JedisPubSub { @ Override public void onMessage ( final String s , final String s2 ) { } @ Override public void onPMessage ( String s , String s2 , String s3 ) { } @ Override public void onSubscribe ( String s , int i ) { } @ Override public void onUnsubscribe ( String s , int i ) { } @ Override public void onPUnsubscribe ( String s , int i ) { } @ Override public void onPSubscribe ( String s , int i ) { } } }

Fix:
long stamp = Long . parseLong ( entry . getValue ( ) ) ;